I have heard that fetal heart rate bear a relation with the gender of the baby. less than 140 bpm indicates a boy and vice versa. how far is this true?

Not true.: All the indirect "signs" of fetal gender are old wive's tales; if you want to know your baby's sex, just get an ultrasound (or even blood test nowadays such as maternit21/harmony). There is no scientific proof that male fetuses have lower baseline heart-rate in comparison to females. Gender does not affect fetal heart rate variation. Oguch o, steer p. Br j obstet gynaecol. 1998 dec;105(12):1312-4.